Eliminating corrosion due to galvanic current set up by dissimilar metals in the presence of an ionized solution



March 18, 1952 P. w. UHL ELIMINATING CORROSION DUE TO GALVANIC CURRENT SET UF BY DISSIMILAR METALS IN THE PRESENCE OF AN IONIZED SOLUTION Filed Sept. 26. 1949 @ffl KZ/if Patented Mar. 18, 1952 ELIMINATING CORROSION DUE TO GAL- VANIC CURRENT SET UP BY DISSIMILAR METALS IN THE PRESENCE F AN ION- IZED SOLUTION Peter W. Uhl, Detroit, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporationof Delaware Application September 26, 1949, Serial No. 117,916

7 Claims.

This invention has to do with eliminating or inhibiting corrosion due to galvanic current set up by dissimilar metals inthe presence of an ionized solution or electrcylte.

The invention will be described in its application to inhibiting corrosion between adjacent surfaces of aluminum and ferrous metal and in connection with cooling systems of internal combustion engines, althoughin its broader aspect the invention has application to other metals and/or other systems.

It has been found, for example, that aluminum water manifolds bolted to a cast iron engine with conventional gaskets therebetween (neoprene, for example), corrode rather severely, particularly over a small. section of the inside of each flange of the aluminum manifold through which the cooling water passes. In explanation ofv this, aluminum or aluminum alloys are electrcpositive to cast iron or steel. At their junction in` contact with water containing minerals and each other, the positive section of the electrocouple thus formed tends to corrode and waste' away.

In .accordance with my invention corrosion between adjacent layers of dissimilar metals in the presence of an ionized solution or electrolyte is eliminated or inhibited by interposing a rectifying plate or gasket between the dissimilar metals. The rectifying plates may be of any known materials employed as current rectiers. Typical examples are: copper-copper oxide, copper-copper sulfate-magnesium, iron-selenium, etc.

Preferably, in order to ensure good electrical Contact between the rectifier and dissimilar metals, thin layers of relatively soft materials or metals which are conductors of electricity are interposed between the rectifier and dissimilar metals. Representative examples of suitable contact layers are: thin tin or lead discs; electroplated metal, sprayed metal, sprayed aquadag (colloidal graphite in distilled water), etc.

Inthe accompanying drawing there is illustrated the preferred'embodiment of the invention as applied to aluminum and ferrous metal employed in the cooling water systems of internal combustion engines.

Figure 1 is a View of a portion of an aluminum cooling water manifold and cast iron engine cylinder head having cooling water passages therein and a rectifying gasket between the aluminum and cast iron.

Figure 2 is a perspective View of a rectifying gasket.

Figure 3 is a sectional view on line 3-3 of Figure 2 on an enlarged scale and additionally (Cl. 12S-41.71)

showing tinfoil on each face of a rect'i'fyingV4 gasket;

Figure 4 is a sectional view of aiixtur'e ein'- ployed in the cooling water system of test enlgmes.

In Figure 1 of the drawing there is shown a portion of an engine cylinder head I0` of cast iron having a passage I2 therein for cooling water. Between the head and a cooling water manifold I4 of aluminum is a rectify'in'gl gasket indicated generally by l ii.Y The recti'fyig gasket (see especially Figures 2 andv '3) consists o'f' a layer of sheet copper I8 having one face thereof oxidized to form thereon a thin layer ZUof copperoxide, specifically cuprous oxide, coext'ensi'v'e with said one face of the copper sheet. On tlie'two faces of the rectifying gasket areY provided: two similar thin tin foil gaskets 22to provide Contact surfaces for the aluminum and cast' iron; In the form of gasket shown in Figure'S'the copper sheet is in thickness, the layer of copper oxide is .003" in thickness, and the layers'of tin foil are 1/64 in thickness. TheseV relative dimensions are given for purposes of illustration and not of limitation.

Since a rectifier acts in effect as a valve and permits eiective current flow in only one direction (in the case of copper-cuprous oxide the direction of current flow is from the oxide to' the copper) it might be thought thaty the rectifier would eifectively inhibit corrosion o'f aluminum only if it were so placed as toy opposeciirrent flow as the result of galvanic coupling of' aluminum and ferrous metal. However, tests indicate'this is not so and it is immaterial which one4 o'f'the two faces of the rectifying `gasket isa'dja'c'ent the aluminum as the corrosion thereof due to galvanic action is substantially eliminated" in either event. If desired a plurality 'ofthe rectifying gaskets may be interposed between the aluminum water manifold and cast iron.

Figure 4 illustrates a fixture' employedin the water cooling systemused' for engine tests: In thisfigure the parts are not all drawn'to" scale in order that'the arrangement of partsmayjbe more clearly shown and described.' The'fixture consists of a multipjlicity of discs or'wa-'shrs of cast iron and aluminum with rectifyingl gaskets (in some cases neoprene cr neoprene-asbestos gaskets are employed as noted on the drawing) and tin washers between the cast iron and aluminum. In some instances, as noted on the drawing, the copper-oxide layer of the rectifier is adjacent a cast iron disc and in other instances it is adjacent an aluminum disc. The discs of cast iron and aluminum and rectifying and other gaskets and tin washers are clamped together by two steel plates 30 secured together by a plurality of bolts 32. The multiplicity of cast iron, aluminum discs, gaskets and washers havealigned openings in the centers thereof so that when they are clamped together a continuous cooling water passage 34 is provided in the fixture. A coupling 36 is screwed into each plate 30 and the couplings are adapted to have connected thereto pipes (not shown) of the water cooling system of test engines whereby the heated water could flow therethrough. When connected in this way the test fixture was used over an extended period of time in connection with engine tests. The water used in the tests was normal city water containing salts or minerals in solution and consequently was an ionized solution. Judged from practical field experience on actual engine failures, the fixture should have failed in parts in from one to three months. However, the fixture developed no visible failure in approximately seven and one-half months of operation which shows protection was afforded by insertion of rectifying plates, or gaskets, in the assembly. After being operated for approximately seven and one-half months the fixture was disassembled and the parts examined and the following facts and observations noted:

1. Where rectiers were in contact with aluminum, no corrosion of the face was apparent.

2. Where neoprene-asbestos gasket material was in contact with aluminum, the aluminum showed some evidence of attack on the face.

3. Where tin gaskets were employed between aluminum plates, or between aluminum and cast iron, no noticeable corrosion occurred.

4. Where neoprene-asbestos gaskets were employed between aluminum plates, some corrosion of faces occurred. When placed between cast iron and aluminum, some corrosion occurred on the face of the aluminum with no noticeable attack on the cast iron.

5. Corrosion products between neoprene-asbestos gaskets and aluminum were white colored.

6. The water passage tube of the assembly was uniformly coated with about le" of a fairly hard reddish-brown scale.

7. Removal of scale by reaming with a 1/2" reamer; operated by hand, showed less corrosion or attack on parts adjacent to rectifier plates.

8. Evidence of excessive corrosion was ab'sent from the entire assembly. Based on the results of the test, the assembly would undoubtedly last for years.

I claim:

. 1. An internal combustion engine having a water cooling system including a cooling water manifold of aluminum and a cast iron engine part with a cooling water passage therein, a coppercopper oxide rectifying gasket between the aluminum manifold and water passage in the cast iron engine part, a layer of tin foil contacting one face of said rectifying gasket and aluminum and a second layer of tin foil contacting the other face of said rectifying gasket and the cast iron.

2. A gasket comprising a layer of copper and a thinner layer of copper-oxide bonded thereto, said gasket being adapted to be connected in uid tight relation between a cooling water manifold of aluminum and a cooling water passage in a cast iron engine part.

3. In a device of the class described, a part formed of aluminum, a part formed of ferrous metal, and a copper-copper oxide rectifier between the aluminum and ferrous metal and electrically connected to both, said parts having an ionized solution in contact therewith.

4. In a device of the class described, a part formed of one metal, a second part formed of another metal, one of said metals being electronegative with respect to the other and said metals having an ionized solution in contact therewith, and a current rectifier between the l(glissimilar metals and electrically connected to oth.

5. An internal combustion engine having a water cooling system including a cooling water manifold of aluminum and a cast iron engine part with a cooling water passage therein, a current rectifying gasket between the aluminum manifold and water passage in the cast iron engine part, a layer of tin foil contacting one face of said rectifying gasket and aluminum and a second layer of tin foil contacting the other face of said rectifying gasket and the cast iron.

6. An internal combustion engine having a water cooling system including a cooling water manifold of aluminum and a ferrous metal engine part with a cooling water passage therein, a current rectifying gasket between the aluminum manifold and water passage in the ferrous metal engine part, a layer of soft metal contacting one face of said rectifying gasket and aluminum and a second layer of soft metal contacting the other face of said rectifying gasket and the ferrous metal.

'7. In a device of the class described, a part formed of one metal and having a uid passageway therein, a second part formed of another metal and having a fluid passageway therein, one of said metals being electronegative with respect to the other and said passageways having an ionized solution therein, and a current rectifying gasket between said parts electrically connected to both and also connecting in fluid tight manner the passageways in said parts.v

PETER W. UHL.

REFERENCES CITED The following references are of record the le of this patent:

UNITED STATES PATENTS Number Name Date 528,318 Bailey Oct. 30, 1894 2,179,293 Hein Nov. 7, 1939 2,189,617 YSiebert Feb. 6, 1940 2,395,833 Bagwell Mar. 5, 1946 FOREIGN PATENTS 5 Number Country Date 30,130 Netherlands Jan. 16, 1933 

1. AN INTERNAL COMBUSTION ENGINE HAVING A WATER COOLING SYSTEM INCLUDING A COOLING WATER MANIFOLD OF ALUMINUM AND A CAST IRON ENGINE PART WITH A COOLING WATER PASSAGE THEREIN, A COPPERCOPPER OXIDE RECTIFYING GASKET BETWEEN THE ALUMINUM MANIFOLD AND WATER PASSAGE IN THE CAST IRON ENGINE PART, A LAYER OF TIN FOIL CONTACTING ONE FACE OF SAID RECTIFYING GASKET AND ALUMINUM AND A SECOND LAYER OF TIN FOIL CONTACTING THE OTHER FACE OF SAID RECTIFYING GASKET AND THE CAST IRON. 